We use molecular simulation to study the selective adsorption of BTEX mixtures (benzene, toluene, ethylbenzene, xylenes) in metal-organic frameworks. The adsorption of these compounds is a basic step in reutilizing petrochemical industry derivatives. BTEX mixture components are precursors to polymers such as poly(ethylene terephthalate). It is also important to store these molecules due to their high toxicity to humans. We study the storage, adsorption selectivity, distribution, and overall behavior of the adsorbed molecules inside the structures. We use MOF-1, MIL-47, and IRMOF-1 to test the effect of the size of the cavities and the topology of the structure in the adsorption of the components of the mixture. We found that these structures are useful to separate ethylbenzene and o-xylene from the BTEX mixtures.